In an organic light emitting device (hereinafter, referred to as an “OLED”) display, a liquid crystal display (hereinafter, referred to as a “LCD”) , and the like, usually it is preferable that the display have a wide view angle such that a good image can be obtained when an observer sees the image from any position.
On the other hand, for example, in the case where a person performs work in a commuter train, sometimes the person needs to prevent other people from taking a look at the inside of a screen. In such cases, it is desirable that the view angle be controlled such that the screen can be seen only from the observer of the display while the screen cannot be seen from other people. In order to meet such the demand, for example, a louver type view angle control sheet is developed and used as shown in FIG. 10. The louver type view angle control sheet exerts an effect that an outside light beam is blocked to enhance contrast. For example, there is disclosed a view angle control sheet in which generation of a double image (referred to as ghost) is decreased in the louver (see Patent Document 1 to Patent document 3). FIG. 5 of Patent Document 1 is an explanatory view of the ghost.
Patent Document 1: Japanese Patent Application Publication (JP-B) No. 58-47681
Patent Document 2: Japanese Patent Application National Publication No. 6-504627
Patent Document 3: Japanese Patent Application Laid-Open No. 9-311206